Tapio Takala

Sound rendering

We present a general methodology to produce synchronized soundtracks for animations. A sound world is modeled by associating a characteristic sound for each object in a scene. These sounds can be generated from a behavioral or physically-based simulation. Collision sounds can be computed from vibrational response of elastic bodies to the collision impulse. Alternatively, stereotypic recorded sound effects can be associated with each interaction of objects. Sounds may also be generated procedurally, The sound world is described with a sound event file, and is rendered in two passes. First the propagation paths from 3D objects to each microphone are analyzed and used to calculate sound transformations according to the acoustic environment. These effects are convolutions, encoded into two essential parameters, delay and attenuation of each sound. Timeciependency of these two parameters is represented with key frames, thus being completely independent of the original 3D animation script. In the second pass the sounds associated with objects are instantiated, modulated by interpolated key parameters, and summed up to the final soundtrack. The advantage of a modular architecture is that the same methods can be used for all types of animations, keyframed, physically-based and behavioral. We also discuss the differences of sound and light, and the remarkable similarities in their rendering processes. CR

Creating interactive virtual auditory environments

We survey sound rendering techniques by comparing them to visual image rendering and describe several approaches for performing sound rendering in virtual auditory environments.

Comparison of auditory, visual, and audiovisual navigation in a 3D space

A navigation test was carried out in a spatially immersive virtual environment. The test was a gamelike experience where the task of subjects was to find as many gates as possible while they navigated through a track guided by auditory and/or visual cues. The results are presented as a function of the number of found gates, searching times, and normalized path lengths. Audiovisual navigation was clearly the most efficient. Visual navigation was second and the auditory navigation the least efficient. Further analysis of travel paths indicate that auditory cues were utilized in the beginning to locate the next gate; a visual cue was the most important in the final approach to the gate.

Virtual musical instruments — natural sound using physical models

Physical modelling of musical instruments is an exciting new paradigm in digital sound synthesis. The basic idea is to imitate the sound production mechanism of an acoustic musical instrument using a computer program. The sound produced by such a model will automatically resemble that of the real instrument, if the model has been devised in a proper way. In this article we review the history and present techniques of physical modelling. It appears that the many seemingly very different modelling methods try to achieve the same result: to simulate the solutions of the wave equation in a simplified manner. We concentrate on the digital waveguide modelling technique which has gained much popularity among both researchers and engineers in the music technology industry. The benefits and drawbacks of the new technology are considered, and concurrent research topics are discussed. The physical modelling approach offers many new applications, especially in the fields of multimedia and virtual reality.

Modelling transmission, immunity and disease of Haemophilus influenzae type b in a structured population

An individual-based stochastic simulation model was constructed to study the epidemiology of Haemophilus influenzae type b (Hib) transmission, immunity and invasive disease. Embedded in a demographic model, the transmission model of Hib carriage employs the most important social mixing patterns with three types of contact sites (family, day-care group, and school class). The model includes immunity against invasive Hib disease, initiated and boosted by Hib carriage and cross-reactive bacterial encounters. The model reproduces the observed age patterns in Hib carriage and disease in Finland before large-scale use of the Hib conjugate vaccines. The model was used to investigate characteristics of Hib transmission. The analysis emphasizes transmission between children and adults in families while pointing out the importance of pre-school and school-aged children in maintaining Hib circulation. Carriage in these age groups is thus identified as being essential to target for sustained effects of interventions by vaccination.

Voluntary pupil size change as control in eyes only interaction

We investigate consciously controlled pupil size as an input modality. Pupil size is affected by various processes, e.g., physical activation, strong emotional experiences and cognitive effort. Our hypothesis is that given continuous feedback, users can learn to control pupil size via physical and psychological self-regulation. We test it by measuring the magnitude of self evoked pupil size changes following seven different instructions, while providing real time graphical feedback on pupil size. Results show that some types of voluntary effort affect pupil size on a statistically significant level. A second controlled experiment confirms that subjects can produce pupil dilation and construction on demand during paced tasks. Applications and limitations to using voluntary pupil size manipulation as an input modality are discussed.

Indirect protection obtained by Haemophilus influenzae type b vaccination: analysis in a structured population model

We used a structured population model to study factors determining the magnitude of indirect protection in Haemophilus influenzae type b (Hib) vaccination. On a simulation platform mimicking the population of Finland, a Hib transmission and immunity model, including cross-reactive bacterial encounters, was formulated. Utilizing different vaccination coverages and vaccine types we could study how fast the incidence of Hib disease declined due to direct and indirect vaccination effects. With the Finnish vaccination schedule we could reproduce the observed disappearance of Hib cases. Our results show that an indirect effect was already significant with a relatively low vaccine coverage, even with a vaccine only partly reducing carriage acquisition. This suggests that the vaccination schedule and vaccine to be used should be chosen to result, in addition to immunological memory, in high antibody concentrations, sufficient to reduce carriage, the latter being the main factor behind successful elimination of transmission and disease.

Possibilities and limitations of immersive free-hand expression: a case study with professional artists

We have studied the usability and artistic potential of an immersive 3D painting system in its early state. The system allows one to draw lines, meshes and particle clouds using a one-hand wand in a virtual room with stereoscopic display. In its more mature state the software will allow for two-handed interaction with new interaction devices. Ten professional artists participated for two days each in a test, performing both given tasks and free artistic sketching. Their experiences were collected through observation and interviews. At this stage, we found that common technical limitations of virtual environments, such as latency and tracking inaccuracy as well as clumsiness of the hardware devices, may considerably hinder handicraft work. On the other hand, every single participant felt that immersion offers new potential for artistic expression and was definitely willing to continue in the second phase of the test later this year.

Some aspects of role of audio in immersive visualization

We define four different tasks which are common in immersive visualization. Immersive visualization takes place in virtual environments, which provide an integrated system of 3D auditory and 3D visual display. The main objective of our research is to find out the best possible ways to use audio in different tasks. In the long run the goal is more efficient utilization of the spatial audio in immersive visualization application areas. Results of our first experiment have proven that navigation is possible using auditory cues.

User Interface Management System with Geometric Modeling Capability: A CAD System's Framework

Since practical designing involves both ¿bottom-up¿ and ¿topdown¿ approaches, a CAD system should be able to cope with all types of data.